1. Field of the Invention
The present invention relates to a process for calculating estimated vehicle speeds on the basis of wheel speeds of the vehicle wheels and a longitudinal acceleration/deceleration value detected by a longitudinal acceleration/deceleration sensor to a value obtained by adding an offset value corresponding to an output error. The offset value includes a slope component and a dispersion component of an output from the longitudinal acceleration/deceleration sensor.
2. Description of the Prior Art
A process for calculating an estimated vehicle speed is conventionally known, for example, from Japanese Patent Application Laid-open No. 28045/90, which uses a value resulting from addition of an offset value corresponding to a gravitational acceleration inputted to a longitudinal acceleration/deceleration sensor, i.e., a slope component during traveling of a vehicle on a slope, to an output from the longitudinal acceleration/deceleration sensor.
The output from the longitudinal acceleration/deceleration sensor may be dispersed due to any cause such as a midpoint displacement, rectilinearity, hysteresis, a temperature characteristic and a mounting error. In an error of the output from the longitudinal acceleration/deceleration sensor, it is necessary to take into account a large value resulting from the addition of the slope component to the output dispersion component. For this reason, an estimated vehicle speed is determined on the basis of a value provided by addition of an offset corresponding to the output error to a longitudinal acceleration or deceleration determined in the longitudinal acceleration/deceleration sensor, and the wheel speeds. However, if the offset value is always a large value as described above, it can not be said that the accuracy of a control on the basis of the estimated vehicle speed is excellent.